Technical Field
The present invention generally relates to a light-projecting device.
Related Art
A light-projecting device is known that projects projection lights to a projection surface from a light source such as a semiconductor laser to draw an image. With the light-projecting device, when a light-emitting environment of a temperature of the light source, an ambient temperature, and the like changes, a light quantity of the projection lights also changes and shifts from a target light quantity. Because of this, in a situation of performing APC (auto power control) of the light source in the light-projecting device, the light source cannot be illuminated at the target light quantity unless light output characteristics such as I-L characteristics are sequentially updated. Therefore, there is a need to periodically acquire the I-L characteristics.
However, when acquiring the I-L characteristics, the light source is illuminated at a light quantity near a maximum output. Because of this, when the I-L characteristics are acquired in a situation where a light spot of the projection lights is in a display region of the image, noise arises in the image. Because of this, conventionally, APC of the light source is performed by blocking a projection light projected to a region outside the display region and acquiring I-L characteristics of this projection light.
As one example of the prior art relating to one or more embodiments of the present invention, there is the scanning projection display device of patent literature 1. With this device, among lights from a laser light source, a light where a ratio of a scanning angle to a maximum scanning angle is no less than a predetermined ratio is blocked by a blocking unit. Moreover, so an average temperature of the laser light source is the same in each scanning period, controlled is a current that flows in the laser light source while a light from the laser light source is being blocked (light-blocking period).
Patent Literature 1: Japanese Patent Application Publication No. 2013-164503
However, with the method described above, scanning a projection light in the region outside the display region does not contribute to forming the image displayed in the display region. Therefore, a drawing efficiency of the light-projecting device decreases and a perceived brightness of the image formed in the display region decreases. Moreover, to acquire the I-L characteristics, the projection light must be blocked, but in a situation where the blocking unit is configured by hardware, a blocking range thereof is fixed. When the scanning angle is not constant, for example, when the scanning angle is changed to prioritize light quantity, the blocking unit cannot respond to this change. Therefore, blocking to acquire the I-L characteristics will not be able to be performed.